linux-kernel - Re: [PATCH v2 5/5] misc: eeprom_93xx46: Add support for a GPIO 'select' line.

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Date:	Tue, 24 Nov 2015 23:53:09 -0500
From:	Cory Tusar <cory.tusar@...1solutions.com>
To:	Vladimir Zapolskiy <vz@...ia.com>, robh+dt@...nel.org,
	pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org, agust@...x.de,
	gregkh@...uxfoundation.org
Cc:	jic23@...nel.org, broonie@...nel.org, afd@...com, andrew@...n.ch,
	Chris.Healy@....aero, Keith.Vennel@....aero,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/5] misc: eeprom_93xx46: Add support for a GPIO
 'select' line.

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On 11/19/2015 01:05 AM, Vladimir Zapolskiy wrote:
> On 19.11.2015 05:29, Cory Tusar wrote:
>> This commit adds support to the eeprom_93x46 driver allowing a GPIO line
>> to function as a 'select' or 'enable' signal prior to accessing the
>> EEPROM.
>>
>> Signed-off-by: Cory Tusar <cory.tusar@...1solutions.com>
>> ---
>>  drivers/misc/eeprom/eeprom_93xx46.c | 26 ++++++++++++++++++++++++++
>>  include/linux/eeprom_93xx46.h       |  1 +
>>  2 files changed, 27 insertions(+)
>>
>> diff --git a/drivers/misc/eeprom/eeprom_93xx46.c b/drivers/misc/eeprom/eeprom_93xx46.c
>> index 0386b03..375951f 100644
>> --- a/drivers/misc/eeprom/eeprom_93xx46.c
>> +++ b/drivers/misc/eeprom/eeprom_93xx46.c
>> @@ -10,11 +10,14 @@
>>  
>>  #include <linux/delay.h>
>>  #include <linux/device.h>
>> +#include <linux/gpio.h>
>> +#include <linux/gpio/consumer.h>
>>  #include <linux/kernel.h>
>>  #include <linux/module.h>
>>  #include <linux/mutex.h>
>>  #include <linux/of.h>
>>  #include <linux/of_device.h>
>> +#include <linux/of_gpio.h>
> 
> Please double check, adding only linux/of_gpio.h header should work,
> linux/gpio.h and linux/gpio/consumer.h are redundant.

There was an error which turned up on a 0-day build related to this:

    tree:   https://github.com/lunn/linux.git asl_v4.3-rc2-zii-stable-dsa-reset
    head:   c91bad95b39a98e0d06809c4c70c9c26747c874a
    commit: a3e1b85039c722799102366b527b6bab9543e4ac [4/41] misc: eeprom: 93xx46: Add support for a GPIO 'select' line.
    config: x86_64-randconfig-x007-11010710 (attached as .config)
    reproduce:
            git checkout a3e1b85039c722799102366b527b6bab9543e4ac
            # save the attached .config to linux build tree
            make ARCH=x86_64

    All errors (new ones prefixed by >>):

       drivers/misc/eeprom/eeprom_93xx46.c: In function 'select_assert':
    >> drivers/misc/eeprom/eeprom_93xx46.c:342:2: error: implicit declaration of function 'gpiod_set_value_cansleep' [-Werror=implicit-function-declaration]
         gpiod_set_value_cansleep(gpio_to_desc(edev->pdata->select_gpio), 1);
         ^
    >> drivers/misc/eeprom/eeprom_93xx46.c:342:27: error: implicit declaration of function 'gpio_to_desc' [-Werror=implicit-function-declaration]
         gpiod_set_value_cansleep(gpio_to_desc(edev->pdata->select_gpio), 1);

I'll re-check with v3 (where everything uses the gpiod_*() interface) to
see if this can be eliminated...

>>  #include <linux/slab.h>
>>  #include <linux/spi/spi.h>
>>  #include <linux/sysfs.h>
>> @@ -344,6 +347,20 @@ static ssize_t eeprom_93xx46_store_erase(struct device *dev,
>>  static DEVICE_ATTR(erase, S_IWUSR, NULL, eeprom_93xx46_store_erase);
>>  
>>  #ifdef CONFIG_OF
>> +static void select_assert(void *context)
>> +{
>> +	struct eeprom_93xx46_dev *edev = context;
>> +
>> +	gpiod_set_value_cansleep(gpio_to_desc(edev->pdata->select_gpio), 1);
> 
> I would suggest to use gpio_set_value()

v3 uses gpiod_*() throughout.  This also addresses an issue where flags
were not being tracked and used properly...

>> +}
>> +
>> +static void select_deassert(void *context)
>> +{
>> +	struct eeprom_93xx46_dev *edev = context;
>> +
>> +	gpiod_set_value_cansleep(gpio_to_desc(edev->pdata->select_gpio), 0);
> 
> Same here.

As above.

>> +}
>> +
>>  static const struct of_device_id eeprom_93xx46_of_table[] = {
>>  	{ .compatible = "eeprom-93xx46", },
>>  	{ .compatible = "atmel,at93c46d", .data = &atmel_at93c46d_data, },
>> @@ -385,6 +402,15 @@ static int eeprom_93xx46_probe_dt(struct spi_device *spi)
>>  	if (of_property_read_bool(np, "read-only"))
>>  		pd->flags |= EE_READONLY;
>>  
>> +	ret = of_get_named_gpio(np, "select-gpios", 0);
> 
> gpios or gpio? I see only one requested gpio.

gpios - for consistency.

>> +	if (ret < 0) {
>> +		pd->select_gpio = -1;
>> +	} else {
>> +		pd->select_gpio = ret;
>> +		pd->prepare = select_assert;
>> +		pd->finish = select_deassert;
>> +	}
>> +
>>  	if (of_id->data) {
>>  		const struct eeprom_93xx46_devtype_data *data = of_id->data;
>>  
>> diff --git a/include/linux/eeprom_93xx46.h b/include/linux/eeprom_93xx46.h
>> index 92fa4c3..aa472c7 100644
>> --- a/include/linux/eeprom_93xx46.h
>> +++ b/include/linux/eeprom_93xx46.h
>> @@ -21,4 +21,5 @@ struct eeprom_93xx46_platform_data {
>>  	 */
>>  	void (*prepare)(void *);
>>  	void (*finish)(void *);
>> +	unsigned int select_gpio;
> 
> Same questions as in v2 4/5.

I simply see it as more straightforward to keep all platform-specific
data together, rather than mix-and-match between eeprom_93xx46_dev and
eeprom_93xx46_platform_data...

Also, the private eeprom_93xx46_dev structure has not been allocated
prior to parsing for DT bindings (without additional restructuring of
.probe() logic).

>>  };
>>
> 
> --
> With best wishes,
> Vladimir
> 


- -- 
Cory Tusar
Principal
PID 1 Solutions, Inc.


"There are two ways of constructing a software design.  One way is to
 make it so simple that there are obviously no deficiencies, and the
 other way is to make it so complicated that there are no obvious
 deficiencies."  --Sir Charles Anthony Richard Hoare

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